Bimetallic Single-Atom Catalysts for Electrocatalytic and Photocatalytic Hydrogen Production

Electrocatalytic and photocatalytic hydrogen evolution reactions (HERs) provide a promising approach to clean energy generation. Bimetallic single-atom catalysts have been developed and explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on their supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H2 production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions. Further mechanistic and synthetic studies on bimetallic single-atom catalysts will be imperative for developing optimal systems for efficient and sustainable hydrogen production.